In an image forming apparatus such as a multifunction peripheral, warming-up processing for raising the temperature of a heat roller of a fixing device has been performed. In the warming-up processing, heat generation of a heating device (e.g., a fixing lamp) is maintained until the temperature of the heat roller reaches a target temperature. In recent years, in order to adapt the image forming apparatus to a stricter energy saving standard, there is a demand for a reduction in time until the temperature of the heat roller reaches the target temperature (hereinafter referred to as “reaching time”). Therefore, a configuration for increasing temperature rising speed is adopted.
However, if the temperature rising speed is increased, overshoot (over temperature) after the temperature reaching the target temperature is likely to increase.